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From: edler@cmcl2.NYU.EDU (Jan Edler)
Newsgroups: comp.unix.wizards
Subject: Re: Information on BSD 4.[23] on two/multiple processor systems
Message-ID: <18673@cmcl2.NYU.EDU>
Date: Thu, 6-Aug-87 17:00:36 EDT
Article-I.D.: cmcl2.18673
Posted: Thu Aug  6 17:00:36 1987
Date-Received: Sat, 8-Aug-87 12:31:58 EDT
References: <1112@elrond.CalComp.COM>
Reply-To: edler@cmcl2.UUCP (Jan Edler)
Organization: New York University, Ultracomputer project
Lines: 120
Keywords: BSD 4.[23] Multiple Processor Systems

By now, quite a few decent quality multiprocessor UNIX systems have
been produced.  I'm sure my list is pretty out of date by now, but I'm
sticking a few references at the end of this message.  I'll let the
various vendors of such systems speak for themselves about details.  If
you want good performance with fairly little work, you should go with
one of them.

If you want to roll your own, it isn't too hard to get something simple
going (like a master/slave system), provided you are already pretty
familiar with the UNIX kernel and with various issues of parallel
programming.  But getting high performance is a lot more work.

Here at NYU we have developed three multiprocessor UNIX kernels, and
are working on a fourth.  The first was a master/slave system based on
v7, the second was a symmetric system also based primarily on v7, the
third was a master/slave system based on 4.2bsd, and we're now working
on a more aggressive symmetric system based on 4.3bsd.  As an
intermediate stage of this new version, we're also doing a "floating
master/slave" system, where most of the kernel is only executed by one
processor at a time, but it isn't always the same processor.

Schemes like master/slave are relatively easy because they work by
trying to preserve, to a great extent, the uniprocessor semantics that
are assumed throughout a standard UNIX kernel.  The better you do that,
the easier the job, but when you serialize things you sacrifice
performance, especially as the number of processors increases.  If your
application mix is not kernel-intensive, it can still give quite good
performance.

A more parallel kernel requires extensive modifications to eliminate
those uniprocessor assumptions.  Some of the references below already
do a reasonable job of explaining this.

In many cases the job of producing a multiprocessor UNIX kernel is also
tied up with the mundane issues of porting to a different machine,
possibly with a different MMU, etc.; these factors should not be
ignored.  There are also a host of additional issues that arise if you
are interested in larger numbers of processors; critical sections that
are entirely acceptable on smaller machines can become easily become
bottlenecks.

Here are some references:

%T The U\s-2NIX\s0 System: Multiprocessor U\s-2NIX\s0 Systems
%A M. J. Bach
%A S. J. Buroff
%J AT&T Bell Laboratories Tech. J.
%V 63
%N 8
%D Oct. 1984
%P 1733-1750
%K unix bltj 3b20
%X Good description of basic approach to a symmetric UNIX kernel

%T M\s-2UNIX\s0, A Multiprocessing Version of U\s-2NIX\s0
%A John A. Hawley,\0III
%A Walter B. Meyer
%R M.S. Thesis
%I Naval Postgraduate School
%C Monterey, California
%D June 1975
%K hawley munix unix pdp11
%X Possibly the earliest project to put UNIX on a multiprocessor.

%T A Dual Processor \s-2VAX\s0 11/780
%A George H. Goble
%A Michael H. Marsh
%R Tech. Report TR-EE 81-31
%D Sept. 1981
%I Purdue University
%K master slave unix vax multiprocessor
%X An early master/slave UNIX system that attracted a lot of attention.

%T VLSI Assist in Building a Multiprocessor U\s-2NIX\s0 System
%A Bob Beck
%A Bob Kasten
%J Proc. USENIX Conf.
%D Summer, 1985
%P 255-275
%K sequent balance 8000 dynix unix

%T A Multiple CPU Version of the U\s-2NIX\s0 Kernel
%A Eric J. Finger
%A Michael M. Krueger
%A Al Nugent
%J Proc. USENIX Conf.
%D Winter, 1985
%P 11-22
%K masscomp unix

%T The Design of the U\s-2NIX\s0 Operating System
%A Maurice J. Bach
%I Prentice-Hall
%C Englewood Cliffs, New Jersey
%D 1986
%K unix internals book

%T Considerations for Massively Parallel U\s-2NIX\s0 Systems
on the NYU Ultracomputer and IBM RP3
%A Jan Edler
%A Allan Gottlieb
%A Jim Lipkis
%J Proc. USENIX conf.
%D Winter, 1986

%T An Overview of the NYU Ultracomputer Project
%A Allan Gottlieb
%R NYU Ultracomputer Note #100
%I New York University
%C New York
%D 1986
%K ucn100

----------------------

Jan Edler
NYU Ultracomputer Project
edler@nyu
...!cmcl2!edler
(212) 998-3353